Abstract: A plastic hollow preform is drawn through a mold passage formed in a closed mold by applying a generally constant suction to a downstream end of a conduit having an upstream end connected to an output end of the mold passage. A flow cross section of the conduit is varied between its upstream and downstream ends so as to vary a rate at which the preform is drawn through the passage by the suction. The flow cross section is varied by displacing a valve element in the conduit between positions in which it differently blocks flow through the conduit.

Abstract: Hollow articles of thermoplastic synthetic resin are produced by suction-blowing in an apparatus in which the shaping is decoupled from the extrusion. A preform handler, especially a six-axis robot, engages the preform at the extrusion or coextrusion head and carries it to the closed mold into which the preform is sucked by suction generated in the mold cavity. While shaping is effected in the mold, extrusion can continue at the head to form a further preform.